Kent Fate ( as opposed to Kent V) was Classic Strange's equal.
He basically has
Superman level physicals
Captain Atom level energy / matter manip
TP and TK on the very high end ( peak feat is pushing a planet with TK into it's sum)
PLus his magic that would be a little ( maybe) below Classic Level Strange but above any other version of Strange. Basically he could call on the power of any god ( good or evil) and at his peak feats reality warp. His best feats were recreating and rebuilding all life on Earth after it was destroyed during his battle with Totec. Recreating the universe that was warped into a surreal spartial plane of nothingness by Ynar and Vandeamon.
Kent Nelson would obliterate void if they both operate at peak levels. I'd say he surpassed Nabu when he was at his height. Kent V. Nelson in some of his later runs was pretty broken as hell too.
Even as a Rookie he
1. Defeated a hell lord in their own dimension
2. Defeated Lady Blaze when her power was amped as she had taken all of purgatory and was half way through taking hell from Neron with her brother
That aside in JSA he discovered that the Helm was like a library of magic and simply gave him the spell he needed when he needed it. he went away to learn this and did. When he returned he casually returned the dead to life, and in doing so fought hundreds of former versions of himself in another dimension. That part and several others were off panel and we only saw them in thought /dream sequences remembering them.